Frankenstein Conquers the World (1965)

In the aftermath of World War II, a scientist in post-war Germany conducts experiments using the heart of Frankenstein. When the heart is irradiated by a nuclear blast, it grows into a giant monster. The creature, known as Frankenstein's Monster, goes on a rampage in Japan, destroying everything in its path. It is up to a team of scientists and military personnel to stop the monster before it destroys humanity.